(a) Field of the Invention
The present invention relates to a mold assembly and a method for encapsulating a semiconductor device, more in detail to the mold assembly and the method capable of encapsulating a semiconductor chip with its surface exposed on the surface of a package.
(b) Description of the Related Art
A conventional method for molding the package of semiconductor chips includes two techniques, that is, a potting technique and a transfer technique.
In the conventional potting technique for encapsulating a semiconductor chip with the bottom surface thereof exposed on the surface of a package, a potting apparatus shown in FIG. 1 is used. The apparatus shown therein supplies a tape 102 reinforced with a frame 101 and moving on the sample stage of a potting device, and applies liquid resin thereto by moving a syringe 103 filled with the liquid resin along the tracks or locus specified by input data. The movement is effected either by the X-Y-Z-direction movement of the syringe itself or the X-Y-direction movement of the sample stage. The liquid resin in the syringe 103 is ejected for application by controlling the pressure of air in a dispenser unit 104.
The liquid resin is expensive and its handling including storage and use thereof is difficult. In addition, the amount of the ejected liquid resin depends on the viscosity of the resin, the pressure of the dispenser unit and a period of application time. The diversity of the amount of the ejected liquid resin generates an unevenness of the thicknesses in the molds. The planarity or flatness of the sample stage also generates the unevenness of the thicknesses in the molds.
Further, in the potting technique described above, some deficiencies exist mainly because no pressure can be applied during the application of the resin. The adherence between the semiconductor chip and the resin in the potting technique is weaker due to the application of no pressure than that in the transfer technique, and peeling-off of the resin at the interface is liable to occur. Further, in the potting technique, in order to prevent a void, the syringe slowly moves to apply the liquid resin, and accordingly a cycle of application time is long and its throughout is lower than that of the transfer technique. When the solder balls on the bottom surface of the tape are disposed outside of the chip (fan-out structure), an inconvenience for the balls may be generated such as co-planarity deficiency and ball missing due to the lower strength of the resin.
In order to remove the above deficiencies in the potting technique, the transfer technique for encapsulating semiconductor chips in a package by the molding is employed. However, the current transfer technique involves other problems such that (1) burrs are generated at an exposed portion and a manufacturing cost rises due to an addition of a step of removing the burrs, and (2) the chip is directly clamped with the mold to generate damages in the chip.
In view of the foregoing, an object of the present is to provide a mold assembly and a method for encapsulating a semiconductor device in which the molding for encapsulation preferably used in the transfer technique provides no burrs.
The present invention provides, in a first aspect thereof, a mold assembly for molding a semiconductor chip including: first and second mold halves disposed for relative movement with respect to each other in a first direction for closing and opening the mold assembly; and a mold releasing member disposed between the semiconductor chip and one of the first and second mold halves, the mold releasing member having a first surface in contact with the semiconductor chip during a closed state of the mold assembly, the mold releasing member having a property of being released from one of the first and second mold halves after molding by a resin, the first surface being larger than a surface of the semiconductor chip in contact with the first surface.
The present invention provides, in a second aspect thereof, a method for molding a semiconductor chip in a mold assembly having first and second mold halves disposed for relative movement with respect to each other, the method including the steps of: sandwiching a mold releasing member and the semiconductor chip between the first mold half and the second mold half, the mold releasing member having a property of elastically deforming, the releasing member and one of the first and second mold halves defining a cavity for receiving the semiconductor chip therein; and injecting resin in the cavity by using a first pressure lower than a pressure, which allows the mold releasing member to elastically deform, in a closed state of the mold assembly to thereby mold the semiconductor chip.
In accordance with the first and the second aspects of the present invention, the use of the mold releasing member can prevent the generation of burrs because the edges of the surface of the semiconductor device is in contact with the film.
The above and other objects, features and advantages of the present invention will be more apparent from the following description.